Personally I would call the passing speed and see if there is a response, it may genuinely have been forgotten for a number of many reasons, ATC transmissions regarding other a/c, a near bird strike, etc...
- If PNF responds, he tends to be back in the loop for the duration of remainder of the takeoff, continue as this is the safest option;
- If PNF does not respond, he is deemed incapacitated, actions depend on:
- speed remaining to V1 (a very low V1 on a contaminated runway may require a continued departure as safer);
- ambient conditions (such as LVO);
- runway remaining;
- remember: you are more familiar with a takeoff then a single pilot RTO in a multicrew aircraft, so this may be safer if not entirely ensured of a safe outcome of the RTO maneuver