We do not see an "end point" to Ruby In Steel in terms of functionality. We already have some ideas for features way beyond version 1.5, but, at this stage, we are not discussing any of these in public.
The reason we published the RoadMap to v 1.5 is to show that we are completely committed to constant development of Ruby In Steel. Not only are we developing the software all the time but we also plan to make regular incremental releases available to users, so that you won't have to wait months to get new features or bugfixes. If you followed our original RoadMap (published in May 2006), you will see that we honoured all the steps which we outlined leading to the release of version 1.0. We are doing our best to follow a similar line of development leading to v 1.5. The RoadMap is not an absolute guarantee that all the steps outlined will be met in exactly the order shown but it is our plan to follow the RoadMap pretty closely and to have all the new features (and a few others that are not yet on the RoadMap) implemented by the release of v 1.5.
So, between now and 1.5 you will see a series of refinements and improvements to existing features (new debugging features, more IntelliSense, better support of server and database technologies etc.) - and also, between 1.1 and 1.3, significantly better support of Rails development, debugging and IntelliSense.
In terms of upgrades. The path to 1.5 is pretty clear: every upgrade is free to registered users.
It's too early to say exactly what the deal will be to upgrade from 1.5 to the version that follows it. What I will say, though, is that we want to make it an 'easy' upgrade. By that, I mean that the upgrade cost should be easy enough on the pocket to make sure that you'll want to move to our next version rather than start looking around for somebody else's software...
p.s. We don't plan any versions 1.6, 1.7 etc. If we make any 'minor' additions after the release of 1.5 those updates will be free too. Any version that required a paid-for upgrade will be significantly different from the 1.x productline. However, as I said, this is looking some way into the future and are our effort is going into 1.x at the moment.