Export/Save as midi file?

Only if you also have Sonar. You'd have to save the pattern in P-Seq, then import the .ptn file into Sonar, where you can convert it to a .mid file. Maybe in the upcoming version of P5, that'll change. Of course, you can import a standard MIDI file.

BTW: Since the pattern file is a superset of a MIDI file, I've tried to just rename the extension to .mid. Sad to say, but cheaters never prosper ...

OK, you're all set. Save the patterns in P-Seq using the third icon over {Save Pattern; Shift+S shortcut], and that'll save it to the Project5\Pattern folder. Then open up the pattern in Sonar by navigating to that Pattern folder in the File/Import menu item of Sonar [switch the file type to .ptn to see it], and it'll import for further processing. You'll have to save it in Sonar as a .mid file in order to bring it back into Project5.

That works well for a single pattern or a single track in P5, but if your P5 project is more complex, you'll have to do a bit more work. Save each individual pattern file in your project (after sending them to track) in P-Seq, as described above. If you desire, change the Pattern Instance MIDI Channel in P-Seq before saving the pattern, and that'll be reflected later in the Sonar .mid file. Create a new blank pattern in P-Seq, and send it to an unused track in the Tracker (only if you wish to change your "master pattern" to a specific MIDI channel). Otherwise, the blank pattern will be set to MIDI Channel (any), allowing for it to contain multiple MIDI channels inside it.

Drag it the length of the song in both the Tracker, and in P-Seq, remembering to move the red End Marker in P-Seq as well. Now carefully reconstruct your entire project within that blank pattern by dragging your individual saved patterns from the Resource Browser onto it in P-Seq. The Snap to Grid settings are your ally here; using Measure will prevent any single pattern from dropping in on anything but a measure boundary. Once you have the "master pattern" the way that you like, save it as a pattern, and then import that one into Sonar using the procedure above. It'll be displayed as a Standard MIDI file, and all of the channels (and individual patterns) will remain separated for editing there.

It's a bit of a convoluted method, but it's easier to actually perform than describe. Let me know if you need any redirection along the way, and I'll see what I can do. HTH

Edit: After reading the updated Hip Hop thread, I understand your direction a little better. You can also just import the patterns into Sonar track-by-track, and reconstruct your project sequence there. (That might be the easier route.) Then export it to SMF.