I just wanted to provide an update to this question in case anyone still stumbles across it. Since this was asked, we introduced some new features around resizing. There are now two options, permanent and flexible.
Permanent resizing allows you to resize your disk space as well as CPU and RAM. As the name implies, this is a one-way operation. After increasing the disk size, you will not be able to decrease it.
Flexible resizing only upgrades your CPU and RAM. This option is reversible and gives you the flexibility to scale up and down as needed.
For more info, check out this article: