I'm wondering the same thing myself, I placed a pre order last week and sent OCUK a message asking if they have a stock ETA but they said they do not have one yet, but would provide me one once they know more.
Quite eager to find out when stock is due as the games I play (mostly cpu heavy MMO's) get a huge performance boost from this CPU, even over my current 5800x.
I know no competitors! website says stock due end of May so OCUK may be the same, but i'll keep my pre-order here so I don't 'lose my spot' if stock provided isn't enough to fulfil all orders