1 master, multiple slaves RF communication
Well, no, if you have a fixed RF channel width (which is the case here), than if you share that bandwidth, you share the bandwidth. So, no way around that. 

Since the IC can't send on multiple channels simultaneously, you'd need to increase the number of ICs to send on multiple channels.

Anyway, your consideration is off-point. You're controlling the nRF24 with an Arduino. You simply won't be able to do offer more than the 2Mb/s that the nRF24 can deal with! Let alone process received data, unless you're really doing impressive things with your Arduino – like throwing out everything that makes Arduino, and low-level DMA'ing data at high rates to the SPI peripheral. 

Update: You changed the master node to a PC. Well, it doesn't change the fact that per channel, you only get one channel worth of bandwidth. So if you don't want to share bandwidth, see my first two paragraphs, and by more transceivers to attach to your PC. Or, of course, buy something that was meant to do high-rate networking, like WiFi.