We do have to remember that they're still early in the design process, so this can all be subject to change.
The original Alternity used a roll under a target number mechanic. They used a "step die" mechanic to modify the rolls, where the total of other dice would be added or subtracted, according to the difficulty.
The new game is going to use an interesting flip of that idea. You have a target number. Attribute and skill ranks are subtracted from that number, making that the new target number. Then you roll a d20, add or subtract the step die depending on how it is modifying things, and if your roll is greater than the target number you succeed at the action.
While the thinking may take a little getting used to in play, it does seem like an easy enough way to handle resolution.This is going to have a degree of success (or failure) as well, and I think that this will add verisimilitude to the rolling. I am all for adding critical success and failure to game resolution because I think it can make the rolls more meaningful. I know that bidding mechanics can do a similar thing, but I think that you lose some of the uncertainty, and degree of success can add a thrill to a particularly well-done die roll.
So, we're starting to get an idea of how the mechanics will shape up for the new Alternity game, and I think that is good. Since the nature of this new game precludes using the old mechanics that means we need to see how the new game will work. I'd like to see some character creation information up next, hopefully a sample with enough meat to it that we'll get an idea of what characters will look like, and be capable of, in the new game.
It looks like science fiction/fantasy gaming is getting its turn at a resurgence, between the return of Alternity, EN Publishing's role-playing game N.E.W. and Paizo's science fantasy game Starfinder. Since science fiction is one of the genres that I enjoy most, I am excited to see that my tastes are getting some love from RPG publishers.