It means the instructions for the 1065 are still in draft form. https://www.irs.gov/pub/irs-dft/i1065--dft.pdf
You can still file, BUT once IRS issues the final instructions their MIGHT be changes.
Does it actually prevent e-filing? I e-filed a partnership return a couple of weeks ago with ProSeries and it wasn't an issue.
when the message reads that the forms could change if the instructions change, and amendment would be necessary, I'm reluctant to file. Yes, to be honest probably can, but I'm not into amending partnership returns. I have one with 50 + partners.....ouch