Not necessarily. Most shelter cats have been exposed to the herpes virus at some point. Yes, it is contagious and there is a possibility that a new cat could contract it but it really depends on the immune system of the other cat as to whether or not they will show symptoms. I have 6 cats. 2 of those are siblings (Max and Tyson) that came in with the herpes virus. Tyson has flare-ups (his immune system is compromised, he also has FLUTD and is prone to bladder infections, among other things.) Max, however, has not had any flare-ups since he was 5 wks old...they are 2.5 yrs now. My other 4 cats have been exposed to the virus but they have not shown any symptoms.
However, since you are aware of the needs of a herpes kitty, I of course would encourage you to consider adopting another one. =)
My longest resident cat has herpes. We have since adopted 2 kitties and neither of them have it. Most of the times, kitties pick up herpes at a crowded shelter and/or because they are malnourished and their immune systems are at risk. Herpes has actually become more common in the past several years and most cats have been exposed to it at some point in their lives. Not all cats will show symptoms. Some act more like carrier cats and only have flare ups at intensely stressful times. Others have it more severely all the time and some have a flare up every once in awhile.