My opinion is that Srila Prabhupada will not be happy with these senior devotees going outside of ISKCON.
Srila Prabhupada has said that everything is in his books. If you try to understand this, then by the mercy of Srila Prabhupada it will all be made clear to you.
It is a fact that if an elevated vaiṣṇava is there, then one should go and take his association. There is no harm in that. But in this case, there is a danger that the discipline in our organization will be affected adversely. If the leaders are going outside of ISKCON, how will we be able to maintain discipline? Srila Prabhupada has formed this society, and this threat to his society will only cause him pain. With this consideration, they should not go. That will only lead to indiscipline in our society.

Two sides are there, philosophical and organizational. On the organizational side, this practice is not good. Therefore we have this GBC body, which makes so many rules to maintain the discipline of the members of our society. But how will we be able to keep discipline now? No one will listen — “If the leaders are going, why should we listen? We will also go.” This will create only trouble."