With genetic engineering, nanotechnology, advances in medicine and drugs, plus the social structures we have in place, there’s no telling.
For example, we could (potentially, anyway) engineer a few super-humans, free of the various diseases that plague us now, with superior intelligence, strength, whatever. It wouldn’t take many breeding pairs (assuming heritability of the modified genetics) to branch off in relative isolation (at least breeding isolation) to create a new species. Or we could species-wide make a conscious decision to not do that at all.
But since our evolution can be self-directed, there’s no reason to think that it’s inevitable that we will evolve, biologically. Over larger populations, we do seem to be evolving, at least statistically, into “less” than we once were (as a species). That is, as our economies improve (which they generally do over time, notwithstanding little blips such as the past few years) and our health care and delivery systems along with that, as well as our abilities to cure or at least put into remission various diseases that prevent offspring from reaching sexual maturity and producing offspring, we have more and more “culls” (to use a term that may be offensive, but is still accurate) that would never have survived in the wild—or even in our own frontier days—but actually thrive now.
So who knows? We could be supermen, or we could be weakened idiots, or anywhere in between.