I must digress as I would love a true pancake.While I also think that a f6.3 pancake isn't as convincing, I wouldn't get the Sigma 30mm DC DN. The Sigma 30mm is a huge Aps-c lens. I would rather get the Sigma 45mm f2.8 or 24mm f3.5.
If it does typical beautiful Lumix bokeh like both my 24-105 and 70-300 zooms it's a winner and f6.3 doesn't matter. This is referencing my tests of faster legacy Pentax primes against both zooms and despite being slower the bokeh is nicer on Lumix zooms.
I'm not one for wanting to totally cream out backgrounds anyway and a pancake f6.3 whether mountain hiking or city street photography sounds brilliant, especially downtown where a big lens puts me off even doing photography.
I discovered with Lumix zooms that the less bokeh was nicer than the faster Pentax legacy primes as they painted the background nicer, I said this on the legacy lens thread earlier.
I really hope this f6.3 pancake is not just rumour as I'll love it