No, otherwise the show would last for 4 hours and it's too late for the random people watching the contest
I think 26 is good. Even now with 26, sometimes the show is getting boring to me!
For the semis and total number of participants, there does need to be a limit. A total of maybe 52 would be more than enough for a potential maximum. That would be 26 countries in each semi, ten qualify in each for the final along with big five and hosts, which would also have 26 countries.