Yes there will be sidequests with a time limit. I'd say about 50% of the sidequests I designed up to now have a time-limit or a time-based element to them (things like, if you manage to find the lair of the bad guys within 10 days you can rescue all the hostages, if you take longer they've been killed by the bad guys, so you get a sub-optimal resolution for the quest (killed the bad guys but didn't rescue the hostages, gain a lesser reward than if you had rescued the hostages in time)).
Not going to spoil any actual quests yet, but you'll see a huge variety in sidequests. Some will have no time limit, some a generous time limit, some a more pressing time limit, some will have minor elements that change based on how long you take (like, a guide offers to show you the way but he'll only stay in town for a week, if you don't take up his offer until then you'll have to find the way yourself), some will be quick and simple affairs, others will have multiple quest stages to them, some will be centered on stealth, some on combat, some on exploration, some on NPC interaction.
If there's one thing you can be sure about, it's that you'll find a lot more interesting and varied quests than just generic "go to X and kill Y" or "deliver X to Y" fare.
But those simpler quests will also exist, of course, because the point of variety is that it's varied.