Playing without a main striker is definitely dangerous but the players that Real Madrid have can be relied on because every player is very talented so as long as Real Madrid can field with this starting XI, they will not understand the lack of a main striker. Mbappe is most likely to be signed by Real Madrid if they are secretly signing a player. A few days ago, there were strong rumors that Real Madrid had secretly signed an agreement with Mbappe. It is natural that this matter will remain secret since it is said to be a secret agreement. I'm just waiting for the transfer window to open next season because that's when we'll know exactly where Mbappe's next destination is going to be.
In the end Carlo Ancelotti had to maximize the existing stock of players, even though the risk was very big. But Madrid had no other options for now, overall Madrid only lacks a pure striker figure, in other sectors Ancelotti has quite a lot of options. Jude Bellingham became an alternative solution for the Italian tactician, when Madrid needed a goal-hungry striker. What many Madrid fans concerns have been answered, Madrid is still leading the top of the standings. By having an even squad depth, the absence of a pure striker can be covered.
Regarding the Mbappe rumors, I don't know yet for sure, as you said everything will be open when the transfer market starts again.