Full trailer here. There's not too too much to pore over here, but here are my off the cuff thoughts as a bona fide Shiori Sicko:
- Difficult to know which version of the game this is based off at least in terms of raw base content. Most likely it's PS1 since that's historically the most representative and iconic version domestically here in Japan. Saturn had more content, but nothing super impactful and it arguably diluted the original design intentions of the game in spots. The original PCE version has a handful of exclusive bits, but also some slightly racier CGs, which word on the street says is the main reason it wasn't localized for the Mini. Basically, I would be very shocked if it offers anything more than the PS1 game in terms of actual events and minigames (though there are things I would argue they should absolutely cherrypick from other versions if they really want to please hardcore fans; I for one say, bring back the Pocket exclusive girls!)
- While there isn't that much to dissect in terms of gameplay changes, they have clearly added a few new widgets that weren't present in any other version of the game, including the PSP port, which kinda offered some modest stuff here and there. I have mixed feelings about them and hope they'll at least be optional because for as much as I'm in favorable of tweakable difficulty, the original Tokimemo was also very much so designed to not have all of the under-the-hood info divulged to players so that they would learn to use social cues and whatnot to figure things out intuitively. Most curiously, they've surfaced the biorhythm stuff, which as I've always understood it, is basically the series' term for the fluctuating RNG. Girl's Side games I believe have always made this information available in some capacity, but that was never the case with a mainline Tokimemo game. I'm not against its inclusion per se, but without a toggle, I fear it could really trivialize the overall gameplay loop and especially Shiori runs, which IMO, aren't that hard once you've done a few runs with other girls and know what to expect.
- Beyond the optional updated visuals, the implementation of EVS, or Emotional Voice System, where the girls vocalize your character's name, is obviously the headlining feature. While it has its roots officially in Tokimemo 2, where it was something of a technical marvel, the dev team has gone on record saying that they had wanted to do it with the original game all the way back on the PCE and ultimately scrapped it for technical reasons. So while this is definitely a longtime ambition finally fulfilled, there is still a potential caveat depending on how Konami implements it. The last time a mainline Tokimemo game included EVS was 4 on the PSP, which just offloaded the voice generation stuff onto an online server that's obviously long since been shut off. My hope is that they just do what I think they've always done with Girl's Side and the Love Plus games at minimum and just have at least a big list of fixed, prerecorded names and then some generic nicknames for anything else bases on initial consonant/vowel sounds. Though in my heart of hearts, it would be nice to see them do some proper offline generation again a la 2; the tech may never be perfect, but it already works surprisingly well there, surely the Switch can do it even better 25 years later.
- Odds of localization? I'd peg it at 50/50 whether it's already been planned/is actively being worked on. The existence of this remake was something of an assumed given, but even in a post-Tim Rogers world, it's hard to say what calculus Konami's bean counters are using, even if I would personally argue it was a safe bet and especially with the right people involved, wink wink.
(Please don't ask me anything more on this end; this isn't me teasing anything, I know literally as much as anybody else.)
Why they didn't announce this thing three months ago during the anniversary concert, I couldn't tell you, but however this thing turns out, you can be sure I'll be there for it day 1 and will probably discuss it further as we learn more and more. 
