How about growing them in a pot?

I am thinking of buying caladium bulbs on sale this year, but, not actually planting them until next spring. Will they still be viable? Can I leave them in their box in an indoor closet until then?

you have to plant the corms and grow them this summer. do it in pots.
otherwise they will dry up by next spring.
it is already too late as is - they take close to 2 months to develop good roots and leaves - and then the summer is over and they won't grow when soil temps drop to below 65F. and they don't like day temps below 70F - that will trigger decline.
it's a very bad idea to buy corms that late in the season, unless you'll be growing them in greenhouse come fall.
what you could do is buy potted leafed out plants in pots - at any time in summer and let them grow till they decline in fall (pots or ground). then overwinter in pots. and replant next spring.
it's best to start them shallow and in pots on heating mat like begonia tubers - the roots need 70F temps to grow well. then you can plant them out in the garden.
of course, now that it's warm a sunny window sill will serve as a heating mat of sorts. the reason you need to start shallow and warm - they are very rot prone just like begonias. you need to water them just right until they have 1st few leaves. and outside they will just rot if it's rainy all the time and cool.