I think the chances of SIDHE making another Rugby code game is extremely large. I have never seen so much talk for one game in people I know and some people I know (aadults) purchased this game as their first ever.
Now that the next batch looks to be becoming popualr as well, HES and SIDHE shall be reaping in the benefits, which will just improve technology and budgets. So if there were a sequel or a Union game, it would just be better.
The experience that the staff have now of an RL online community and making an RL game combined with the new things will just make the next game bloody awesome and I hope it becomes a yearly thing!