It's not mentioned much but I think that Tales of Berseria release one month before will probably help Persona 5, there's probably a good overlap between the audiences and Berseria served as a wake up call for all the PS3/PS4 owners out there, now one month after Berseria many of them should be able to move on to their next game and not just play your usual Pazudora Granblue etc. when commuting to/from work.
There's also FFXV delay which might slightly help, before there was going to be 3 big JRPG in a 5-6 weeks time frame with Persona 5 being sandwiched between the two others, with FFXV delay I think that leaves enough time for your old time JRPG fan, something like
"Oh there are these three games I want, I'll buy the first one since it's released much earlier, the second and third are released close to each other though maybe I want to play FFXV first and I'll just buy a second-hand copy of Persona 5 later on this year"
And the Slim launch of course, but rather than more overall sales I think it will mostly contribute to higher sales for the PS4 SKU at the expense of the PS3 SKU.
By themselves each fact do not account much, but combined together they will definitely help its momentum and FW sales (by how much ? Who knows, could be 10k could be 50k...)
Also it's been said multiple times, but the game would've sold much better had it been released on PS3 back in 2011-2012-2013