Adding the Bitcoin symbol to the keyboard will scream "ADOPTION". The question is where to put the key? I would suggest they replace the $ with the bitcoin symbol... just kidding. However, it gotta go somewhere, what do you think?
Bitcoin symbol is already added to some iOS and Android digital keyboards, but you can create your own version for desktop keyboards using shortcuts.
I know some software programs that can reprogram or remap your keyboard keys on base level and replace it with anything you want including bitcoin symbol shortcut.
To make it even better you can print your own Bitcoin transparent sticker, or order custom key with bitcoin symbol (I would replace it with key that I don't use often).
I didn't saw anyone making this DIY project, but it would be interesting to make one if I found some free time.
