Maybe we should just say “YMMV”, but it probably doesn’t have much to do with Gigabit networking. Remember, these are 802.11n devices, which means they are relegated to a relatively slow network scheme.
More likely your device will determine how many cameras you can view at once. Remember the days of having low-end Android users check to see if hardware acceleration was engaged to eliminate jerkiness in the video playback?
For a quick idea of how networking might (or might not) come into play, read this thing I wrote awhile back. In short, it may depend on how much OTHER traffic you have on the network (or how slow or efficient your device hardware is, as mentioned above). So YMMV: