One thing I fear about the current VR development trend is that they're going for these shorter experiences and not even entertaining the idea of real staying power, which is what VR actually needs right now. Not that 4-6 is bad, but you also have to look at the type of game that it is. It's a linear shooter with the story as a big draw. After you've played it, you've probably experienced a majority of what it has to offer.
If this game was to be a true success I'd say it would at least need a fairly fleshed out horde mode, otherwise it could get buried in the sea of short but entertaining experiences that you play through in one sitting and never pick up again. Especially with PSVR where games are fewer and further between, there need to be more games that keep you interested for long enough that there aren't huge slumps in between.