Its not going to be Borja. I would be incredibly shocked if it was. IMO, there is zero chance that STP chooses someone that is essentially a one-trick pony after having as versatile a singer as Weiland. Just like how Dean doesn't use a telecaster for every song, STP wont pick a singer that is only accomplished at one style to do a very wide reaching catalog that encompasses Bossa Nova, Rock, Pop, Glam, Country, etc.
Borja's power and ability to do heavier material definitely rightfully earned him an audition spot. He is absolutely talented. I think Borja could be a great fit for a new band with some of the STP members (a la Army of Anyone) but considering the existing catalog, I feel pretty confident that STP knows they need someone that is a bit more versatile. I dont care who here says they're in the know, until we hear an announcement nothing is decided.