Yes, that is how it worked this last time. Obroan became purchasable with unranked comms, while brutalizer requires the matching Obroan piece and ranked comms.
You could max out unranked, convert them all to ranked at the vendor right there at the PvP mission terminals until you have ranked maxed out, then go back to maxing out unranked. That way you don't have to shelve anything. You'll be grinding for the Brutalizer pieces you'll need to trade for the next tier after the update.
If you're dead set on shelving your toon until the update, I suppose that would be one way, but maxing unranked, converting to ranked and buying the Brutalizer pieces now lets you continue playing that toon, increasing his gear now while building your valor. You won't have any lapse in play because you'll still be grinding Brutalizer gear through your unranked conversions.
Classic comms aren't necessarily useless. I've geared out most of my comps on several toons with 162s from classic comms. My guess is that we'll see similar moves in gear/comms as we did at the last level cap increase.
I guess I don't understand the desire to shelve a toon. If you want to play a different class/race, that's a personal choice, obviously. I, personally, feel that you'd still have fun and be doing yourself a favor by meeting the current level cap on any 50s you have and then running Oricon with help. On PoT5, there are usually a few people who are willing to help run people through the initial story missions there to get you your 156s. That's how I've done it. This game is much more fun when you play with friends, whether from in-game or out.
Up to you, obviously. I know people don't like duplicating efforts, but as it has been previously stated, the new level cap, if it comes, won't be for 3-4 months IF everything happens in a timely manner. I would suggest you keep progressing as if there was no new level cap coming. I mean, do you want to stay behind the power curve every time a major change is announced/implemented, or do you want to roll into the new update maxed out and ready to get the jump on people like you who waited?