But that only counts if all factors remain the same. If the ROI is high the MN count will increase and the average ROI might go down.
You are right.
However the fact is in both two scenarios, Ultima is actually un-profitable masternode coin at the moment and might be the same in the future.
To some degree there is always this first mover advantage. DASH for example became damn big with their master nodes and there won't be many getting to where DASH is today. It becomes less exciting over time.