Autofocus with 1.4x converter

I am pondering over buying the Pentax 50-135mm/2.8 and the announced and very soon to be released Sigma 50-150mm/2.8 for my GX-10.
There appears to be little difference in IQ, especially in normal usage rather than lab conditions.

I have a Sigma 1.4xTC. As the Sigma only has HSM(SDM) focussing only (no screw) and the TC does not support this then I assume I will only have manual focus if using the lens with a TC?

Assuming that the Pentax fits onto the TC without the rear element catching, then as the Pentax supports SDM and screw focussing I presume that it will focus using SDM when mounted on the camera, and will revert back to screw when used with the TC, is this correct?

I do not see myself using it regularly with the TC as I do have a longer lens, and I am 90% certain that I am going for the Pentax anyway, but I just needed this final piece of information to finish my research.

Tim

Another thing in favour for the pentax, weather sealing.

also, that Sigma has been "soon to be released" for quite a few months now.

I have the 50-135 and the Sigma 1.4X TC - you don't need to worry about Auto- or Manual focus issues with this pair... Because they cannot be used together. The rear element of the 50-135 is in the perfect position to be scratched or worse by even attempting to fit the two together.

I have a Tamron 2X MC7 that allows manual focus, and the Pentax 1.7x does autofocus (if you set the lens focus at the midpoint rather than infinity) but I've discovered that the sharpness of the 50-135 to be good enough that cropping the TC-less photo has always been better (in my limited experience)