Sheridan, it's still a little too early to tell but I think that's a spike. Is this one of the huge Dends you're talking of? Could it be an Antelope Dend? These get huge. I've got one that's over 3&1/2 ft. tall and growing taller with each new cane. It flowers all year long, no winter rest. And the average Phal type Dends can get huge, also. Dends come in all sizes. The mini's are cute too, have a few and really enjoy them.
As for re-potting, it's always best to do this when you have new root and/or cane growth which I see you do, so now would be a good time . The problem with Dends is their massive root bound growth and freeing the roots from the medium. I'd definitely advise soaking the plant first and what doesn't fall away, just pot up into the new container. When I received my Antelope Dend., it was impossible to even remove the pot so the entire plant (pot and all) went into the next size container and it hasn't suffered the least for it.
Hope this helps.
P.S. Give Archie a big kiss for me!
New Really Big Dendrobiums What to Do?
The taller they get the more top heavy they are. S/H seems like a perfect fit because it makes the pots heavier. The medium doesn't look too bad. I'd wait and repot to S/H. They really resent repotting so the less often you do it the better they like it. 
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