Pretty good rumour roundup from warseer;
Ogre Magic has been reworked and spellcasting now works the same way as for all wizards. Spells are pretty much similar to what they used to be, except they last until next magic phase and are not RIP. Lore attribute is bloodgruel - on 2+ mage gains 1 wound and +1 to cast for his next spell, on a 1 takes an S6 hit.
Ogre mages can take great maw, death, heavens and beasts magic.
New mage model is the firebelly, who uses lore of fire, costs araound a fifth more than an empire cannon, can be upgraded to lvl 2 for the standard price of a wizard upgrade, can take a great weapon or extra hand weapon and has S4 breath attack, flaming attacks and 4+ ward vs fire.
Magic items and big names:
Big names still there and come out of magic item allowance. Didn't get changed that much from what you currently have. Best one is probably giantbreaker - doesn't require giant in the army - for the cost of dispel scroll model can't refuse challenges or flee but gets +1S.
Magic items are few and generally meh compared with common items. Thundermace basically gives you one thundercrush attack just like the sphinx has for a ton of points. Most interesting item is hellheart, which causes a miscast in all enemy mages within 5xD6" at the beginning of enemy magic phase - one use only, costs 2 scrolls.
Core units now include ironguts at five points less than they used to be, and with all command models costed at +10 points (which is same across the book).
You can get 40 gnoblars for the cost of one dark elf sorceress, and they come with throwing weapons attached and no prerequisites.
Special units got a lot of changes, leadbelchers will now fire D6 shots every turn, no misfires, and are move and fire with no penalty for moving. They cost one point less than Yhetees, which cost one point less than talisman of preservation.
Maneaters are half an empire cannon in points, and basically choose two special rules (you cannot chose the same special rule for two units) from a group of 8 - including poisoned attacks, sniper, stubborn, swiftride, strider, vanguard, itp, scout.
Mournfang cavalry is the new heavy cav, with a lot of options (potentially a 2+ armour save), tons of attacks and a price tag that is in the vicinity of a bloodcrusher, depending on what armour/weapons you take. 3 wounds, D3 impact hits and a total of 7 attacks per model make them somewhat fearsome.
Gorger is now special and gets a bit more expensive, but loses the rule by which it had to end movement closer to an enemy unit. It does have frenzy, unbreakable, killing blow and ambusher special rules.
Scrapalauncher is rare, slightly cheaper I think and similar to what it does now (S3 KB catapult)
Ironblaster is an empire cannon with horrible fluff and a pretty unpleasant misfire chart. It is nearly as expensive as a hydra, but has move and fire, S10 grapeshot and a special rule that allows you to roll two dice for bounce and chose the highest, even if one is a misfire.
The two mammoth-like critters are:
the stonehorn, which can have a mounted harpoon launcher (S6 D3 wounds 36" bolt thrower that doesn't penetrate ranks and is move and fire if mounted), 4+ armour save, does a lot of S6 impact hits on the charge, has dragon-like stats (but lower WS, Ld and initiative), M7, 4+ armour save and a special rule which halves the damage from all multiple-wound weapons that hit it.
the thundertusk, which is a support version of the above - has a mounted catapult that doesn't get hurt in any way by misfires, a harpoon and a 12" S6 KB weapon (chaintrap) - 3 weapons on its back, and gives all enemy models within 6" ASL. The tradeoff is - no impact hits and one less attack.
Both of these big beasties cost as much as around 5 wraiths.
A stonehorn can also be the mount for a hunter, which costs almost as much as a high elf prince.
Last but not least: the sabertusk. Special unit, 1-10 unit size. Each one has 3 S4 attacks, so aside from being the redirector of your dreams, it can sometimes work as a mage assassin. One costs slightly more than 4 halberdiers. T4 and two wounds.
They can't use general's leadership or battle standard re-roll, and their own LD is 4 - and can only be joined by a hunter - so I would say they will only come in two unit sizes - 1 or 10+hunter. This second option is not so bad - the unit will cost you some 350 points, but it has vanguard, swiftstride, and 30 S4 WS4 I4 attacks + whatever the hunter brings.
Looking forward to the release! August is going to go so slow.... at least there is a 40k tournament to look forward to to speed things up. The firebellies sound awesome, Lore of Fire would be a great lore for Ogres!