Unless they already have the mark 2s in development. Surely no company releases product and assumes "this is it. It will never be better than this, so we won't even try to improve it."
I'd imagine the mark 2s are already being worked upon, and the mark 3s only awaiting the results of some technical development that they predict won't be acheived for a good few months. In the meantime, they've got robots to sell and a market eager for them now. Hence- mark 1s.
SBT