Not yet. Getting good incremental search performance would likely require someone to write a plugin in c that loads files into a big optimized data structure. There may be a way to hack vim to run grep over the whole database each time you hit a key, but that would probably not be fast enough.
For an example of an open source vim plugin that does incremental search (on filenames, not file contents unfortunately), you could look at the command-t plugin:
Another technical constraint that one might run into if one tries to load a whole database of notes into vim buffers is that each user is by default limited to 1024 simultaneously open files, and many note databases contain more notes than that. The limit can be lifted fairly easily, but users should not have to deal with such things.