I will start of by saying that I know nothing about FD-SOI, or the reasons why Silicon On Insulator is not being used as much as it once was, royalties perhaps.?
If FD-SOI gave a 10% power drop for a 10% price increase then that could be a reasonable tradeoff, not least because the general rules (to my knowledge) usually allow for a 10% clock-speed increase instead of a 10% power decrease. However there could be a number of other issues along the way, such as the verification process, which is often very long would require a substantial committal by whoever chose to use this process, additionally the a Fab company would require a substantial contract.
What I see as possibly happening is one manufacturer taking the plunge whilst everyone else looks on, the others will wait and see the outcomes and either undercut the company using FD-SOI and thus (possibly) destroying the market instantly, or others will join the fray. As far as I understand the market and the Fab'ing industry this is all planned well in advance and takes a colossal amount of money, time and effort to realize, and I suspect whether companies chose to use this technology is dependent on a very large number of possibilities.
Just my take, with little real knowledge of the situation.
fd is for fully depleted.
amd and ibm both used SOI, amd dropped soi for bulk at 28nm. not sure why.
there is a cost premium using soi over bulk but there are a range of uses from servers to mobile where the premium of using silicon with higher initial cost pays off in lower energy costs over the long run.
i'm sure spcr and mobile and data centers would be willing to buy a premium cpu with soi for lower power.