I prefer to think of this as not, "The Beginning of the End", but rather, "The End of the Beginning".
By that, I mean that we have got over the getting to know the SGSII, phase. We hardened flashers now know the in's and out's of the phone. We know its capabilities... and its limitations. We have gone through all the trials and tribulations of Gingerbread. The testing of custom ROM's. The selection of modems. The configuration of kernels.
Now we have moved on to ICS and, thanks to Gingerbread and the last year of experience, the transition has been easier.
Sure, there are dev's who will be moving on to the latest and greatest on the market. However, let us not forget that there are many millions of SGSII's out there and, when all said and done, the SGSII and the SGSIII are not a million miles apart.
Already we have seen ports of app's, wallpapers, fonts and even parts of firmware come our way from the SGSIII.
I took my foot off of the gas towards the end of Gingerbread and, for about 5 months, I stuck with CheckROM RevolutionHD and just changed my modem and kernel.
I see no reason why I might not find another custom ROM like that, maybe CheckROM v7... maybe NEAT. Who knows? That should take me up to Christmas and no doubt the successor to the SGSIII will be announced with even more goodies and, in the case of the UK, it will be LTE enabled.
Sure, there may be some dev's that we've come to know and trust, moving on but nature abhors a vacuum and I fully expect others to take their place.
As for the slow down in official, stock, ICS releases... that's to be expected. The first release was LPQ which, IMHO, was a real dogs breakfast! I refused point blank to go over to ICS until LP7 showed up... which was bearable. Since then Samsung have been working on the ICS firmware to get it into some sort of shape. With the release of LPW/LPD/LPG they've now gone a very long way to doing that. My feeling is that, by-and-large, we will not see any major improvements or releases for the SGSII now. After all said and done... Samsung are in the business of selling new handsets and the ICS release for the SGSII was a good will gesture to the millions of users. I really can't see them investing any more time, effort or money into the SGSII. Any improvements and tweaks will now come from the dev's... as was the case after Gingerbread, Android 2.3.6, and not from Samsung.
As far as I'm concerned... there's still life left in the old girl yet!