Of course there's no guarantee when there are other players who are much better than him in the same position, and that means it will be very difficult for Rodrygo to secure a starting spot in the team. He's still quite young and there may still be plenty of opportunities for him if he can be patient and continue to improve his individual skills. But if Rodrygo's goal is to play regularly for the national team, perhaps considering other clubs is also a good idea, as long as he can guarantee a spot, as the national team itself has many players in the same position as him.
You are right that he is young and has much of room to improve so being patient could work out for him. But you also made good point that if he wants to play for national team regularly he might need to think about joining another club where he has guaranteed more playing time. This is common problem for talented young players do they stay at big club and fight for chance, or do they move to smaller team to play more and develop faster?
Rodrygo is a young, fast, and high-quality player. He could always play for the Brazilian national team because his manager, Carlo Ancelotti, knows him well. If he doesn't get enough playing time at Real Madrid, it would perhaps be better for him to avoid a transfer to another team. It's difficult to predict his current situation, but I hope the decision he makes is the best one for him.
Rodrigo is a good player who doesn't deserve whs he's facing in his career at the moment in Real Madrid because of the impact he has created in the team but it seems like he is not going to be having a good playing time under Xabi Alonso and as a young player who still has what it takes to continue is good ame it's better he moves to a different place where he will be a regular player so that he will always be called by his national team when the time arrives. Ancelotti is his former coach at Real Madrid and the present coach of his national team it will be better if Rodrigo has a good club where he will be starting so that he will maintain his quality when he is invited by Ancelotti to play for his country Brazil.