When I upgrade it as support, I usually upgrade it to the pink, so it's well worth it.
As for every other time, theoretically, everyone should be placing 1 ward with the support placing 3 + 1 pink, that's 8 wards on the map. If one person upgrades their totem, that gives you 1 extra ward for 1 minute every 2 minutes (if that makes sense). If 2 people upgrade their totem, theoretically, you can either have 2 extra wards for 1 minute, or if they 'stagger' their ward placements, you'll have 1 extra ward up at all times. If all 4 non-supports upgrade their totem and place perfectly, you'll have 10 wards up on the map at any given time (including 1 pink). Fantastic.
Realistically, that's not going to happen. You're gonna have players who forget that their trinket exists, and there's going to be times when you're sitting on a charged trinket but not placing it, even if it's only for 30 seconds or so. If we assume only the support + 2 other players are warding, and that the 2 other players aren't warding 'perfectly' as soon as the trinket refreshes, that's going to be about 5 wards up semi-permanently, and sometimes a 6th up on the map (including 1 pink). 4 of those are likely going to be from the support. If both 'warding' players upgrade their trinket, it doesn't matter if they don't ward perfectly, if they ward within a minute of their trinket refreshing, you'll have 6 wards up permanently, sometimes having 7 for a minute or so and if you're lucky having 8 for about 30 seconds. To me, that's worth it, but only if you're not holding off a major purchase.