I did exactly what you are suggesting, only it was about seven years ago and I got an M3 to go with my D70. I still have both cameras but have never bought another dSLR as I've hardly used the D70 since - though I have quite a few rangefinders now.
From my experience, I would suggest you may find:
1. Feeling a bit underwhelmed at first - is this what all the fuss is about?
2. Enjoyment of the manual, mechanical experience
3. The results you get are not the ones you expected, which can be great
4. Struggling to replicate the results you like
5. Experimenting with different films and developers
6. Trying out different camera bodies - eg to understand the difference between an M2 and M3 etc
7. Trying to learn and apply Sunny16 in non-sunny conditions
8. Accumulating a set of lenses
9. Having much more involvement and enjoyment in photography than before - a real sense of satisfaction when a photo turns out just the way
you wanted it to (not what the camera's automation did)
10. Producing a completely different set of photographs compared to the dSLR
That's what I've found anyway. Since 2007 I've used over 400 rolls of film and have had a great, great time making every single one of those photographs.
At some point you'll produce a photograph that is completely unlike anything you've ever taken before, or could have done with the modern kit. It may be a portrait, or a photo of a park bench where the light and tonality and texture are just so exquisite it thrills you.
Oh, and do get an M3 - the perfect starting point.