(this post was originally a discussion with my eastern philosophy class)
... yes methinks. first, i count on god's omnibenevolence!
1. repentance implies change (regret of past wrongs), which is implicit in the notion of being. being is not what one is and it is what one is not (a sartrean lemma, more of this later). satan hasn't changed, presumably, because he's chosen not to (his "fall" rests on this premise).
2. satan is what it is: satanic. but one cannot invoke satan's "nature" causing satan's being. let's keep in mind that satan has a prehistory: lucifer. & this prehistory of satan would have to be rejected to rule out this possibility (for this prehistory is what causes satan). satan's being cannot be self-ruled. "being" is what one finds as one exists. being is not self-presence to itself (but perplexity to one's being). satan's being is given to the very exclusion of goodness from satan's nature, his avoidance of thinking, of reasoning the good. as a thinking being, even in the heart of evil of satan, there must be a space for guilt (a space which doesn't have to be thought for it to be).
3. this willful avoidance perpetuates satan's "nature" by restricting himself to thinking the good, (feeling the guilt of thinking his fault). so, in a sense, satan is not what he is. being satan means to constantly defer goodness. deferring in time, being time, but time is not ecstatic. that is to say, there is always more or less to being than itself (the unpredictability of the future). satan's "being," as stereotyped and beleaguered as it is, is no exception.
4. satan's possible repentance takes a reversal (of that primeval rebellious act in his prehistory). though he cannot become lucifer (since time & history cannot be undone), one can only speculate that he would take a more subdued role. this repentant angel-who-was-satan wishes no more of his past. he's content with god's forgiveness in oblivion.
will it be time for another proud & inexperienced angel to take his place? only if the bane-&-boon moral state of the universe demands it.
the promise, after the end of history, was a universe of goodness. but is such universe of goodness-without-evil possible after the end-of-the-devil?