See this & the change-log thread, lots of stuff has been fixed, & that's only what people have noticed or bothered to report.
Of course many issues remain, & even some new things have crept in, hard to have rock-solid stability/QC as your team's shrinking around you.
Hard to know if there'll be PR1.4, doubtful, there are still people in the team, but it's even smaller now.
My Lumia hasn't received updates "every other week'.....
There's been more but not heaps more, & all have been small compared to the N9's, & it's usually impossible to know everything they do.
S^3 phones don't get updates as regularly as the Lumias, not even close...

If you're referring to downgrade in the sense of downgrading back to PR1.2, IIRC there's not, & it makes little sense that you'd want to.