Jeffrey Merkey, the lead developer of the MDB Linux Kernel Debugger, was on the mailing list a few days back trying to get MDB added to Linux-Next if Linus Torvalds doesn't accept the debugger for Linux 4.6. However, the Linux-Next maintainer first would need some ongoing kernel maintainer to ask for it to be added rather than Jeff along with some notice of when the code might be ready for merging into the kernel.
Kernel developer Ingo Molnar has come out today actively against the MDB debugger on the LKML thread, "So neither the x86 nor other affected maintainers have acked these changes or have agreed to merge it - in fact there are outstanding NAKs against this tree, which were not mentioned in the pull request. Here's one of the objections by me...which technical objections were replied to by Jeff Merkey by accusing me of trolling...So this tree is very far from being ready and I'm not convinced we want to merge it in its current form."
Ingo Molnar also went on to say he'd rather see improvements to the kernel's KDB debugger rather than the MDB debugger. Ingo believes all functionality provided by MDB could be added to KDB/KGDB and that would be the better solution.