I am curious: how soon shall we espect to have a Ruby on Rails version benefitting from ruby 1.9?
It depends on the confluence of several semi-independent streams.
First, the rails-core team seems to have one person working on 1.9 compatibility.
Second, ruby1.9 itself needs to stabilize a bit before it's ready for serious production work. Matz's team switched the version number from the hoped for 1.9.1 to 1.9.0 shortly before the Christmas release and indicated that 1.9 shouldn't be considered stable. It will probably be a few more months before they release a 1.9.1 version which would be the first 'stable' release. Until then any 1.9 stuff rails or not should probably be considered experimental.
And then there's the question of 1.9 compatibility changes to all the third-party plugins and gems which are used in the many rails applications.
It's all coming, no doubt, but just when is hard to predict.
Thank you for answering. I was eager to know cause I've read wonders about 1.9 performances and was wondering how that would impact on my rails app performance...