Yes, the IRS is already accepting Partnerships (but not S-Corps) by e-file with no pdf attachments.  The CCH tax software has been sending them for almost two months, although only for Partnerships under 50 partners. CCH expects to get larger partnerships to e-file by late June.

After an hour and half on the phone with Lacerte my boss got a response today that Lacerte expects to be able to e-file Partnership K2/K3 forms by June 22. Hopefully they'll meet their ETA, and won't need extra time for the larger partnerships.