Actually my theory is that the Senior Partners apocalypse has occurred by the time of Fray, just not in the way that the SP's wanted it to happen.
The following is a brief explanation of some of the history leading to Fray's time ...
"Then, in the twenty-first century there was a battle. A Slayer, possibly with some mystical allies faced an apocalyptic army of demons. And when it was done, they were all gone. All demons, all magicks, banished from this dimension. It is not known if the Slayer lived, but the demons being gone, she was the last to be called."
I have always assumed that this referred to the culmination of the big apocalypse that the Senior Partners have been planning for all this time. It would makes sense that Buffy would be the slayer in question although that isn't definite (outside of the logic that she is the central character of the slayerverse and would therefore be the most likely candidate to be the slayer that it mentions). In that case then it would be very likely that this is also the final battle that will decide Angel's destiny.
If he survived the battle but didn't shanshu then it is likely he would have been removed from this reality along with all other demonic lifeforms. If he survived and did shanshu then he would have remained here but as a human. There is also the possibility that he just does not survive the battle at all.
The only possibility that he survives until the time of Fray is if he remains a vampire but is taken into a demon dimension. Otherwise i think it is fair to assume that he would not be alive by that point.