There are a few things to consider with this setup:
- zebra danios are very active swimmers and tend to need a lot of horizontal space to really feel comfortable
- zebra danios are also naturally schooling and will likely be more comfortable in a larger group. (Usual recommendation is at least 5 or 6.)
- your catfish appear to be some variety of Corydoras (possibly Corydoras aeneus?) so I don't imagine they'll grow much larger than their current size
- two cory cats don't necessarily need more than 10 gallons of water volume, but I do think that they would benefit from a tank with a larger footprint (more floorspace)
- cory cats are another fish that prefers to be in groups; normally it's recommended to have at least 4-6 although having a pair is definitely better than just having one alone!
- regardless of whether or not you decide to move them to a different tank, if your catfish no longer fit in their cave/hiding place, I would recommend replacing it and/or adding a larger one that they will be able to fit into as soon as you are able
- the type of snail you have may be significant; some snails stay relatively small while others (like "apple" or "mystery" snails) can get quite large and have a fairly high bio-load
To sum it up: You probably have enough water volume for the fish you currently have, but may not have enough horizontal space. If you decide to upgrade your tank, you may want to consider moving up to a 20 gallon and adding a few more fish of each species so that they can school together.