All this chat about whether RTB will be useless or not and whether it should be default etc. is all really unnecessary. At the end of the day you guys have got a system specifically tailored to Blockland whereas Steam is generalised for thousands of different games, that right there is a huge reason for most people to want to continue using it.
If RTB usage does drop off a cliff if/when Blockland is greenlit then it means Steam does whatever RTB does much better and RTB is therefore obsolete. No point trying to guess what's going to happen - chill.