Unless we see an ultrabay slim P-ATA BluRay drive for the T6x series, i don't think the tablet/digitizer will ever happen either. Were would you get the motherboard connection from either way?
Why would Lenovo do upgrades on their "old" systems?
Everything today is about introducing newer and cheaper systems to attract even more customers - and take care of the old system when it comes to warranty service repairs.
I wouldn't mind a digitizer on my 15.0" T60p though. But i kinda expect Lenovo to introduce a bluray option for it, now that it is available for the R61 as an option in PATA, and available for the latest generation (W500 and so on) in 9.5 mm - but SATA.
I would love to see a small Wacom in a T400/500. Hell, this would be the most usable business machine I could imagine.
Making handwritten corrections in PDF files on the fly and fully use MS Office would be fantastic. And the price could be much lower than a tablet PC because of the cheaper display.
Lenovo, give this a try!! Seriously!