There are so many problems in doing a TFTD remake properly that I don't think they'll bother.
Some people prefer TFTD for it's extra touches, and even the insane difficulty, but I think it would be fair to say that the majority of people prefer UFO (compare the forum stats if nothing else - 12,000-odd posts in the UFO:EU forum and just under 4,000 for TFTD and both forums have been up for getting on 10 years now, if not slightly longer!), so if anything it would make more financial sense to do a follow-up to that.
Back to the problem of doing TFTD properly - the diving suits in TFTD are ridiculous given how far you can travel in them underwater as well as the depths you're supposed to be at during some of the missions (they should have programmed some missions so you can only do them in Mag Ion armour). The diving suits would have to be re-imagined to make such movement realistic (some sort of displacement technology build in so you can walk normally rather than just suspending disbelief) or else you would have to swim everywhere instead, which sounds cool and crap in equal measure
A displacement suit from the start would solve the movement problem and then you could have an extra movement penalty if the unit were knocked out by enemy fire or something. I dunno.
There are all sorts of other issues too, but I think silencer has hit it on the head in that it is in the future so technically they can have any starting tech they like - just as long as they lose the archaic diving suits and other elements from bygone eras.
I want to see the inside of the UFO in my avatar.