My thoughts...
I guess I'll be keeping mine since I can't afford the new Axe II. However-
1) I doubt the amp modeling/effects are *that* much better in terms of quality. It would be crazy for a software developer to throw out years of development time and bug fixes to do an/extensive total rewrite of the firmware. I think there are some changes here and there to make room for growth later, but nothing that will affect the sound all that much for us "Vintage" Axe-FX owners. Other than more effects/amp cabs availiable and maybe used at one time, (and new models) I think the quality of the modeling is going to be pretty close, despite new users initial claims of night and day difference. I mean, all you ever hear is how the Axe is "Identical to my tube amp." How much more identical can it get with the new Axe? $2100 better? Doubt it.
2) I think if the older tech is being discontinued, that is actually in a way a favor for current owners. It means that instead of getting a new one from Cliff for a lesser price, owners who want a older model will have to get one used from a current owner. After the initial flood of Ebay sales, the inevitable shortage that will occur with the Axe-II, I bet resale will remain reasonably high, $1400-$1500 for ultra, $1200ish for Standard. guess though. If I do update, I bet the hit won't be too bad.
3) The Axe-FX seems very geared to Studio. Many of the hardware features are nice, but not all that relevant to me, or have workarounds (like the headphone jack, dry out, etc.)
Anyway, I don't post hear often, but that's my take on it...
Chris