About the ROI, it really is gone now, but you have to take into account, that BTC price will likely go up, so even if you lose now, you can gain later. Especially if you've already made an investment in the HW, chips etc.

And about changing the HW for next gen Avalon chips (or any other chips), who is going to make this? Bkk seems to be gone (probably get sick of all the events regarding chips delivery, companies taking advantage of opensource project and giving nothing back) and there seems to be noone (even in the group of those companies, which started their business on this) who is able to make this change.