What can we expect?
We know this much: the new Battleground utilizes the reinforcement system introduced with the revision to Alterac Valley, has resources that can be captured similar to Arathi Basin, and has siege vehicles and destructible structures similar to Strand of the Ancients. Blizzard mentioned that it will be possible for players to parachute behind enemy lines, which seems to be the limit of aerial combat. It will also introduce a new siege vehicle called the Glaive Thrower, which should be familiar to players of WarCraft 3. The Night Elf-themed vehicle hurls three-bladed projectiles, or glaives, in a forward thrust which should be somewhat different from the arcing trajectories of Catapults or Demolishers. We'll have to see what else makes these vehicles different from others when we get to test it out on the PTR.
The reinforcement system works because it ensures that the game won't drag on unnecessarily long. This should help Blizzard along with their plan to make all Battleground matches last a somewhat uniform length of time. The developers are considering making the objectives optional or strategic, as opposed to driving the game towards its end the capturing bunkers or towers in Alterac Valley depletes resources. According to Crygil, "the objectives are more of a strategic choice and less of a "you must cap them all" scenario," and adds that "kudos will be in order for those who manage to take all of the unique objectives."
By kudos he probably also means Honor, as capturing the map objectives provide a steady stream of Honor in addition to providing reinforcement count the way Mines do in Alterac Valley. Crygil notes that "the longer you hold either of them, the more honor you're going to amass - win or lose," which should be enough incentive for players to capture them. Because the objectives are captured, rather than destroyed, it doesn't look like reinforcement count is reduced in this manner. It appears that killing enemy players will be the way to go, making it more of an attrition battle.
There doesn't seem to be much air combat in the manner we expected from Wintergrasp, as Nethaera said that "the airship will have a set flightpath," which means that the airships are on a rail, the only variable being the insertion points players choose. It also appears that only one faction will have access to air strikes at any given time, as the airship is accessible through the hangar, which can be captured. Another aspect of the Battleground that's intriguing is the tease that players "can launch gnomes... over walls..."! We've already gotten a taste of this mechanic in the Flame Leviathan fight, where Demolishers can launch players into the air, and it will probably be similar to that.
Alterac Valley done right?
This is the first 40-man (technically 80-man) instance since Naxxramas in vanilla WoW . If Blizzard executes this correctly, the Isle of Conquest will bring the epic feel of Wintergrasp minus the lag. If the map is done right, there's also more opportunity for combat, rather than the races towards the ends of the map such as what happens with Alterac Valley. In fact, with Generals holed up within each faction's keep, it is very reminiscent of the original 40-man raid Battleground. The difference is that it doesn't appear to be a simple matter to get to them... players will need siege vehicles and bombs or ways to bypass the walls.
Because it has worked so well, the objectives will likely be captured through numbers and proximity similar to how objectives in Eye of the Storm and Wintergrasp can be captured. This means there'll be constant conflict over them. That promises to be fun. Unlike Alterac Valley, where a large portion of the landscape is unused and players can and often do ignore each other on the way to the enemy bases, opposing teams will constantly clash over the different points of interest.
A dose of strategy
Similar to Arathi Basin, there are five points of interest that can be captured. However, not all give the same benefits and it will be interesting to see what combination of objectives confer the most advantage on the map. Because the objectives give different benefits, holding three versus two won't necessarily ensure victory in the same way holding three bases in Arathi Basin is a good formula for winning.
By virtue of its location, the Siege Workshop in the center of the map looks to be the most interesting and valuable objective. It supplies siege vehicles, although isn't the only location that does so... the Docks grant access to Glaive Throwers and the Airship Hangar allows players to parachute behind enemy lines. If teams can capture both Eastern and Western points, can they forego the central workshop? Will capturing the reinforcement-boosting Oil Derrick and Cobalt Mines be enough to stave off a rush of vehicles?