You can use the Keepa graph in order to check the history of sellers. If you go to Amazon and find the Keepa graph, towards the bottom right, you can click "More Historical Data". This will pull up a secondary graph below the main Keepa graph, and this one can show you the history of the New Sellers (see the graphs below).
It can be helpful to look at past trends on Keepa, and to communicate with your supplier about their inventory. If the graph constantly shows a lot of sellers, and then there are very few, and then your supplier got a big amount of inventory in stock and has a lot of Amazon clients, you can expect a lot more sellers to hop on the listing. You can talk to your supplier about how much inventory they have and how much they expect to go to Amazon sellers, that way you can better predict if more sellers will hop on. If so, then you would want to just consider ordering less units to account for the fact that more sellers could hop on.
How can I see how many sellers were on a listing in the past?