Museveni has only one agenda: To take over Kenya and gain access to the sea! He will lick Uhuru's ass if that is what is required. He has enlisted Kagame in the process. If peaceful means don't work, he will engineer chaos and then use the excuse of being landlocked to enter Kenya "to open the road to Kampala" and he will never leave.
The day Uhuru signs a federation is the day Kenya dies. Museveni and Kagame would never allow Kenya to get out of it and will go to war not against a country but against separatists. Yemen is an example.