Apparently this is how the tier drops will work in Coliseum:
10-man normal drops nothing but triumph badges.
25-man normal drops trophy of the crusade, one per boss.
10-man heroic drops 1 trophy of the crusade per 10 attempts remaining on the try (up to 4, apparently)
25-man heroic drop...some amount of regalia per x attempts. Here's my guess on it: in 10 man it drops 4 at the max level. That is one every 12 1/2 attempts. But more importantly, it's scalable to 25 man. 4 items per 10 players scales to 10 items per 25.
Do I think they'll do it quite that way? Yeah, actually, I do.
Let's assume for a second that your guild is the best guild ever, and that you are downing the heroic trial of the grand crusader on 25-man without wiping every single week. This means that you will, at best, get 10 tier tokens per week. You'll also get 14 trophy of the crusade tokens per week (because of course you don't wipe on the 10-man heroic tries either, and do those twice per 25 group)
This means that if you have only 25 raiders, you will need 10 perfect runs to get everyone 4 pieces of that tier gear. This would be a bit less than 2 1/2 months of time, and assumes you're doing it from the onset and that you're getting exactly the right token frequency for your raid.
So what does this actually mean? It means that the best guilds will be geared out in 4pT9.258 as Icecrown is about to be available, assuming that Icecrown is going to come out in 4 months time - which would mean the coliseum will last until the end of the year. It might come out sooner; that would mean that 3.2 would be live for 5 months, and 5 months for the coliseum + onyxia is a fairly long time without significant raiding. I'd honestly expect it to come out a bit sooner than that. But for argument's sake, we'll say 4 months at most.
Now what if you're not a stellar guild? What's the going rate between "Ensidia pwns this" and 'most guilds pwn this'? Well, let's take Yogg. Yogg normal mode took Ensidia 3 days to down (on April 16th). It took Fire & Blood until May 23rd. So F&B would be looking at something like a month from now, give or take, to down heroic Anub' - and that wouldn't be perfect attempts, of course. It'd be even longer to get the Insanity tribute. So we'll say on average F&B-like guilds will get about 20 attempts left, and start a month later.
That means that (if it scales linearly) F&B will see approximately 3 months worth of regalias, and we'll be generous and give them an average of 6 per kill over the lifetime. That's 13 weeks, 6 per week, 78 total. Assuming perfect drops, we're looking at at most 3 tier pieces per player.
What does that mean? It means that if you're a class that desperately wants your 4 piece, you should start figuring out what the best two pieces of 245 gear are that you can get and then go for them. If you're not a class that cares as much (for example: ferals) you should concentrate on getting your off-tier pieces when they drop and getting tier tokens when it makes sense to do so.
Now, here's an interesting observation: for ferals, there's nothing all that competitive in the shoulder or head slots. There is good gear in the legs and chest slot, and interesting gear in the glove slot if you're mostly DPS. So it might work out...mostly.
But in general, I would count on getting two pieces of T9.258 gear at most unless you're significantly progressed or your loot rules favor (your class/spec) for whatever reason. Plan accordingly.