I think it will take at least 1.5 decades for their record to be broken or even more. What Real Madrid managed to achieve is something legendary and that's why no other team will come close soon to actually have a chance to dethrone them.
I also don't think Real Madrid will win UCL in the next 4-5 years because even if they have Mbappe , that doesn't mean they will automatically win again. ( remember when Real had galacticos back in 2003-2008 ? and they never even reached an UCL final ? well that thing seems to repeat with this current team Real is building ).
To be honest, I won't be surprised to see Real Madrid winning the European Champions League again next season and the reasons for me thinking that way are the following:
1 - last season real madrid won the european champions league even without having a good striker, they lacked a striker, but even so the coach found a way and solved the problem temporarily and like the rest of the squad is of great quality they won the league
2 - apart from Manchester City, the remaining teams that in the past were great because they were made up of a squad of great players, are in crisis, they do not have a squad made up of many great players, for example: Barcelona, has become an average team, inter a same thing, juventus the same thing, milan the same thing, manchester united the same thing, bayern the same thing, liverpool the same thing. if we ask ourselves the following:
What are the other teams that have a strong squad like Manchester City and Real Madrid?