Is it true that all Arena and Honor PvP gear require Arena ratings now?
No, although the very best ones do. Savage Gladiator gear are excellent rare quality items that require no Arena points to purchase but cost quite a lot of Honor. These items are also purchasable with Emblems of Heroism, so players don't even have to participate in a single Battleground or Arena match in order to buy them. [EDITED: Removed all reference to Arena requirements for Savage Gladiator gear]
Hateful Gladiator items require more Honor and Arena points and decent performance in Arenas... if you choose to buy them from an Arena Vendor. The gloves, chest, and leg pieces all drop from 10-man Archavon, so you can get Hateful Gladiator items from sheer luck. All Hateful Gladiator pieces, including the shoulders and head, are purchasable with Emblems of Valor. Most casual players will have a shot at Hateful Gladiator gear even without having an Arena team simply by joining a 10-man Archavon PUG.
Even Deadly Gladiator items, the best of the best PvP has to offer, can drop off the 25-man version of Archavon, so again players needn't worry about Arena ratings. The only real pieces that require any true participation and dedication to Arena play are the Deadly Gladiator weapons, and head and shoulder pieces. These are not available through any other avenue but Arena points and personal and team ratings of 2030 or higher.
So contrary to what many players have been crying about, this ironically makes Season 5 the most casual-friendly season and allows even complete carebears to run around in full PvP gear. It makes no sense, but the system is actually much more accessible than any other season before it.
But what about the filler pieces like the belt, boots, and bracers?
Hateful Gladiator Honor pieces do not require any Arena ratings but cost quite a bit of Honor and can be bought in the Hall of Legends in Orgrimmar or the Champion's Hall in Stormwind from the Apprentice Armor Quartermasters. Deadly Gladiator Honor pieces only cost Honor (no Arena Points required) but have moderate personal and team ratings. This means that players wanting the absolute best PvP filler gear must participate successfully in Arenas in order to purchase an Honor item.
Note that since no Arena points are required, players need only to play enough games to raise his or her personal and team rating to the required level and purchase the item. Since personal and team ratings are calculated live, players can become eligible to purchase items as soon as their ratings change with every match.
Should I even bother with Savage Gladiator gear?
It could be much worse. Savage Gladiator items are several steps above the craftable PvP sets but inferior to the easily obtainable Hateful Gladiator gear. With persistence and luck, it's far easier to get Hateful Gladiator pieces off 10-man Archavon or even Deadly Gladiator from the 25-man if you get into a group. It will take much longer (you can only try Archavon once a week) but if you shun PvP, it's definitely the best route.
On the other hand, Savage Gladiator items confer the Gladiator bonuses, which the craftable PvP sets lack. It also has higher Resilience and Stamina as well as sockets. Honor is extremely fast at Level 80 and it's possible to get over 10,000 Honor in a day casually playing Wintergrasp and some Battlegrounds. It will take some time considering the cheapest piece, the gloves, cost 50,000 Honor. I recommend pursuing the shoulder and head pieces first if you are eyeing Savage Gladiator at all. [EDITED: Removed all reference to Arena requirements from Savage Gladiator gear]
Where are the Savage and Hateful Gladiator weapons?
Good question. It seems like Blizzard has decided to restrict Gladiator weapons to the Deadly Gladiator or 2030 level. In the Beta, there were three tiers of weapons similar to how there are three tiers of armor sets, but these lower tier weapons no longer appear to be available. It remains to be seen whether they'll bring them back at some point in the future, although it's not very likely.
Will there be better Level 70 Arena rewards?
No. Go buy Wrath of the Lich King and level up. Level 80 is where it's at.