By switching now, before open source has caught up, the currently closed-source company could attract users and grow greatly now, quite possibly preventing the open source options from ever catching up (and at least greatly delaying that).
This, of course, requires a change in the business model, idea would be that revenue is generated differently, probably much less per-user, but with a great growth in users. It's then an open question which option will generate more profit over the long-term, but it is at least not clear to me that open sourcing now -- when product is way ahead of open source alternatives -- is the wrong decision.
