Ummm I'm not saying we aren't getting an expansion anytime soon. To be honest I don't know when since I'm not Storm8 staff. Only S8 knows but they wouldn't be able to release the info ahead of time. I'm in the same situation with the rest of you regarding land and inventory. This game is new and full of potential so there will definitely be more updates and expansions. Unfortunately I don't have the answer to when and what at this point in time. I have passed in the request for more land to help and members can feel free to drop a request post in Land expansion thread in Suggestions forum.
As for inventory, I am deleting parts to make space whenever I run out of space. I immediately deleted my expansion parts after my last expansion some time back to have more time to collect them again, which I did and deleted again as and when needed. I'm working to upgrade my highrises and inventory so I kept those parts. I deleted my sledgehammers when I ran out of space and didn't have any bricks and hardhats. You should choose which part you want to delete according to your game plan, i.e. what you are aiming to upgrade.
Like what others have shared, I do wish we could have more control over deletion by quantity or sale etc, it would be so much easier to manage my inventory cos lack of inventory space is my constant challenge. Haha now I have to decide which part to delete next..