Talking extensively about how wonderful your product will be without ever making any promises whatsoever is the work of a bullshit artist.

If you can't keep promises, and don't want to bullshit, then talk more about what the product already does.

I can have this major feature done for you, but I'm not sure if it can be done in 2 months, so I say 3 to be conservative.

OR

I can have many small sub-features that relate to this major feature done in 2 months, but I might know exactly which features make the cut in those 2 months.

Seems congruous to me

Both of those are promising specific things with a specific timeframe.