does it make sense to even consider asking FISA to OK this at this time? what happens if they say no?
The President is on record as doing what needs to be done.
Do you think he would respect a "no" answer, when he believe he is asking out of courtesy, not out of need for permission?
Well there's this little problem...
The FISA court has taken it upon itself to issue an edict that they will no longer admit information in a probable cause determination (to obtain a FISA warrant) that was gathered through warrantless intercepts. Never mind that they have no authority to issue such an edict, outside of a case holding.
I say a "little" problem, because most of the President's warrantless NSA intercepts will either remain entirely intelligence matters outside of FISA channels, or over time, they will be turned into criminal matters, for which a warrant will then be sought through the regular court process, again bypassing the FISA courts.
But for a small number of these cases, there may come a point in the intelligence gathering process, for a particular case, where the President may find it more advantageous to now obtain a FISA "warrant" (technically, they aren't called warrants under FISA, they are called "orders").
So because the FISA court has been throwing their hissy fit over the warrantless intercepts, that could throw a road block in the President's plans. That "little" problem needs to be resolved, but I don't think you'll find the President appearing, hat in hand, pleading for a reconsideration of their errant policy. It will be a bit more strident than that.
Wordy, but hopefully informative.