I would say that is not possible, again to optimise the communications it will send on data change where possible but it will only need one change in the transaction telegram and it will send that, the other points will be collisions if other traffic is present, if the tags are grouped and 10,000 tags would probably be split into a number of requests. You have to remember each telegram will have a lot of control information, requests etc. so even a single register read would require a telegram of a considerable number of bytes. As I said before besides the OPC server talking to the PLC, it is also talking to your application this all takes a finite time, depend on network speed, traffic, number of apps running on the PC the list goes on so it is not easy to calculate the times.
Talk to Kepware, although they want to sell you the software and may embellish their reply they may be able to give you some idea. I once spoke to them as I was concerned about amount of data I was intending to gather from multiple PLC's of different kinds and their response was we have a system out there that has over a million tags but how slow that was is anybody's guess You can download a trial that will last for 2 hours, just re-start to get another 2 hours then you can see what update times you are getting.