If memebership is down, what about posting something on the TML? I did a quick TravellerCon search and only found a mention of it once. Before the plug is pulled this year, maybe a plea there can drum up a few memberships?
Failing that, if there is not enough memberships, how about making the Con every two years?
I simply can't make it this year, I am unemployed and the 11-hour drive is a bit much for me, but I still bought a membership just to help keep this alive for when I can make it and run some games.