Bethesda posted a list of fixes that are planned after release and stash size is one of the features being improved on the list. The list they posted is as follows:
Ultra-Wide Support: We will support 21:9 post launch. Once available, or shortly before, we’ll be sure to post our patch notes that let you know when to expect it.
Larger Stash Size: We’ve seen this one come up a lot and understand the frustration. While the Stash size at 400 weight limit can get easier to deal with over time, we do plan on increasing it in the future.
Push-to-Talk [UPDATED]: While we aim to create a consistent experience no matter what platform you’re on, we understand that some of you on PC would like the option for Push-to-Talk. Our goal with voice chat being on by default is to highlight that the world is alive with real people, other players like you. We like to start with encouraging player interaction and will
look into adding this in the futurebe adding this in the near future.
FOV Slider: We haven’t supported FOV sliders in our previous games as it is known to break a lot of animations and causes a lot of clipping to occur onscreen. You do have the option to zoom out in third person on PC by holding View and moving the mousewheel, but we won’t be able to have it for first person view.
Exploits of Various Types: Many exploits we’ve seen reported have been known and will be addressed in a future update.
Issues with social menu and inviting friends/making teams/etc.: Those who were experiencing issues with the social components will find that many of these issues have been fixed. We will continue to fix issues as they arise as fast as we’re able to, so keep letting us know when you run into them.
Hunger not being sated: Some were saying their “Hunger bar” wouldn’t replenish no matter how much they ate or how cleared of diseases they were. This issue has been addressed and will be in a future update so no more hungry dwellers.
Loud Gunshot/Noises: The issue of players hearing sudden random gunshot/loud sounds around Appalachia will be addressed in a future update near launch.