A cynic might suggest that there's not much in it for keyboard manufacturers in making a Bluetooth desktop set, which would enable one part of it to be replaced easily with someone else's it, though there are certainly some out there that use Bluetooth.
The manufacturers would doubtless say that their systems are more robust than Bluetooth, which is better in such a popular and congested bit of airspace.
RS-232 adaptors? Cor blimey mate, don't get much call for those round here... as the serial port has largely withered away, at least outside specialist applications, perhaps no one sees a need to make these adaptors in the quantities that will be necessary to drive down prices.
As for X10, I think the pairing and range issues perhaps counted against Bluetooth there, and earlier versions could be considered a bit over-engineered - you don't really need the bandwidth that's offered.
In the control space, systems like Zigbee and Z-Wave have been trying to establish themselves as replacements for something like X10, though without a massive amount of impact so far - there are still depressingly few Z-Wave bits and bobs for the UK, for instance.
The faster set up time and low power capabilities of Bluetooth Low Energy could make it ideal for that sort of thing, but it'll be competing with all the other standards, and they'll have to create profiles, then get them into kit. Yep, it could be potentially great, if you could buy a new lightswitch and know it'll be compatible with your mobile phone. It could happen - but it's going to take a fair bit of time, I think.
And in the meantime, you might end up with a smart meter that has Zigbee, or a set top box that has Z-Wave; for a while at least, there's going to be plenty of scope for consumers to get thoroughly confused about which bits of kit will work together.