Kakko, Laf, Chytil, Miller, Schneider. There's no telling which of these players will still be here next year--though I would expect most to still be here--but I do expect that they will all improve as they get older. Plus we have other prospects who might come in and make an impact, like Cuylle, Othmann, Lundkvist, Jones.
In a couple years, both Trouba and Kreider will be tradeable, as their NMCs become NTCs. And the cap should go up significantly by then. The next 2 years will be tight cap-wise, but after that, we have lots of options. That's not to say we should wait 2 years before doing anything significant, but at the same time we shouldn't be going all in now.
Right now, unless we can find a deal for the perfect 2C, we should be playing moneyball. No high priced acquisitions. No big trades. Find players who mesh well and help to build a team that is more than the sum of its parts. If we make a big trade for a center and we get it wrong, it's going to hurt us for a lot longer than 2 years.