That sounds like a possible explanation but somehow seems unlikely to me. Business strategy/growth-wise. But yeah, without the prime benefits, the plans don't really seem very attractive. So maybe the really don't want more subs after they reach their target.
My guess is once the dust settles, they will start ripping off just like the rest of them. The 28 days validity as mentioned in the other thread is an example of that. If they really wanted to do good things, they could have lead the change with 30 days. And I also don't think the incumbents are too worried, which is why even their ~345 plans with ~1-2gb/day are limited time only. Once things are back to normal they will settle into their old rip-off mode too. It was a fun ride while it lasted though. Just wish I had converted my vodafone to prepaid 6 months ago. Would have saved quite a bit of money...