It depends what you mean by time. From our faith, as revealed in Scripture, we know that our experience of the heavenly state is to be without end, and without decay or corruption. However, it does not necessarily follow that there will be no perceptible succession of events. In general, orthodox theology has assumed that we will not assume God's own unique attributes - we will not become omnipotent, for example - and so we will not end up "outside time" in the fullest sense, as this is directly and innately part of the God-nature. (I suspect that some of this insistence is in opposition to gnostic/Neoplatonist ideas.) I'm not aware of any sect that holds dogmatically that we will become atemporal, though perhaps some people believe it, or leave it open as an option.
In theology, much of the speculation has historically been guided by the philosophy of Aristotle. In On the heavens 1.9 he writes (my annotations in square brackets):
It is therefore evident that there is also no place or void or time outside the heaven [= beyond the boundary of the universe]. For in every place body can be present; and void is said to be that in which the presence of body, though not actual, is possible; and time is the number of movement. But in the absence of natural body there is no movement, and outside the heaven, as we have shown, body neither exists nor can come to exist. It is clear then that there is neither place, nor void, nor time, outside the heaven. Hence whatever is there [= the Prime Mover], is of such a nature as not to occupy any place, nor does time age it; nor is there any change in any of the things which lie beyond the outermost motion; they continue through their entire duration unalterable and unmodified, living the best and most self-sufficient of lives. 1
This passage indicates that time as such is particular to our world; whatever is outside the world is beyond time. Similarly, Physics 4.12 speaks of a category of eternal things which are not contained in time, measurable by time, or affected by the passage of time.
From a Christian perspective, it is natural to say that God himself ought to be covered by this concept (and while this articulation of the idea is from Greek philosophy, it's not totally un-Biblical). Can other things - heaven, angels, human souls - be considered atemporal as well? If we try to jam Aristotle and the Bible together, we might well think that souls in heaven are outside of time, because they're no longer in the world.
But in general, theologians have been reluctant to say this. Truly being outside of time is reserved for God alone, as an essential part of his nature. Other things may, through the grace of God, be made perpetual or incorruptible or immutable.
Scholastics, who were the first to tackle the topic systematically, came up with various elaborate categories; the most important here is the aevum or aeviternal, which is the kind of relationship to time that the angels have. They are creatures of time insofar as they experience a succession of events, but they do not decay, or age, or change in any essential way. Moreover, God's knowledge of the future was held to be direct, because in a sense he's already there, whereas angels may only make inferences about the future (see Aquinas, Summa Theologica 1.57.3). They are everlasting but not atemporal.
In some writers, the aevum is distinguished from the true eternal in that aeviternal things could be destroyed by God, whereas he himself is immutably immutable. Some sources also note that when the heavens and earth have passed away, there would no longer be an objective way of measuring time, and so the duration of events would be up to our perception alone. This points to a certain "timelessness" of experience, even though there is still a succession of cause and effect.
An influential patristic text is in Augustine's Confessions 11.9,
For, doubtless, that heaven of heavens, which Thou in the Beginning created, is some intellectual creature, which, although in no wise co-eternal unto You, the Trinity, is yet a partaker of Your eternity, and by reason of the sweetness of that most happy contemplation of Yourself, does greatly restrain its own mutability, and without any failure, from the time in which it was created, in clinging unto You, surpasses all the rolling change of times.
nimirum enim caelum caeli, quod in principio fecisti, creatura est aliqua intellectualis, quamquam nequaquam tibi, trinitati, coaeterna, particeps tamen aeternitatis tuae, valde mutabilitatem suam prae dulcedine felicissimae contemplationis tuae cohibet, et sine ullo lapsu, ex quo facta est, inhaerendo tibi, excedit omnem volubilem vicissitudinem temporum.
and another is Boethius, Consolation of Philosophy 5 Pr. 6,
We may say that God indeed is eternal, but the world truly is perpetual.
deum quidem aeternum, mundum vero dicamus esse perpetuum
The exact definition and nature of the aevum was disputed, but the standard account is that of Albertus Magnus in his Summa de Creaturis; the first part, De quattuor coaequaevis, covers the different sorts of time, but the whole text is really one piece. His pupil Thomas Aquinas also mentions the aevum in Summa Theologica 1.10.5-6. For more than you ever wanted to know: The medieval concept of time, ed. Pasquale Porro, BRILL 2001.
1. Translation by J. L. Stocks, 1922.
