Santana is only "in the way" if the rest of the roster is set. This signing is a strong indication that other things are going to happen. My guess is that by Opening Day, there won't be a logjam in the outfield.
On the other hand, the club has five guys for four positions now - Altherr, Herrera, Hoskins, Santana, Williams. Three of them can handle center field; two would be fine in right field (and maybe Santana as well, although I kind of doubt it); two are comfortable at 1B; pretty much any of them can play left.
They could choose to stand pat with this. Each guy sits one game in five? That's not horrible.
It would mean there's no obvious opening for a Cozens or a Quinn - but Cozens may not ever be good enough, and Quinn will probably be on the DL anyway. it would also mean they don't carry a Cam Perkins on the bench (not a bad outcome, IMHO).
So who knows? (My money would be on "something else is pending...")