Sounds like your husband is scheduled for a Modified Barium Swallow Study (MBSS) This test is generally completed by a Speech Pathologist (SLP) with a Radiologist or other MD present. The test is painless - begins with the Patient sitting in a chair or on a stool in the radiology suite. The SLP will give the Patient different consistencies of food and fluid with barium mixed in so that it can be seen as it's swallowed. It's really pretty cool! Completely non-invasive - no pain, no needles, just a video recording of the movement of your swallow as you actually swallow.
The test is to determine primarily if the food/fluid goes in the stomach or if trace amounts enter the airway - called aspiration. This is not a "pass/fail" test - if your husband does aspirate, the SLP will try different consistencies - thicker liquids/ softer foods to see if any specific consistency is more safe than another (meaning less risk of aspiration) If there is still aspiration no matter what kind of food or fluid is tried than the SLP will ask the Patient to complete "compensatory strategies" ie) chin tuck, cough after the swallow and see if that reduces the risk.
So, it's usually up to the SLP to discuss with you the degree of risk - if there is a high risk of aspiration then it may be that food and fluid isn't recommended until the swallow strengthens with specific exercises for a few weeks and then the MBSS may be repeated. If there's mild to moderate risk, the SLP will work with your specific situation to come up with a treatment plan that walks the line of minimizing risk (so not eliminating the risk altogether) and still moving forward on the path to improve swallowing and resume eating orally.

Keep in mind, returning to eating again can be tough - food tastes like crud, feels wierd and can even be a bit scary and overwhelming if the food doesn't move in the mouth the way it should - making one feel like they might choke. The best advice is to work with your SLP, move slowly, keep at it even when it's discouraging, do your oral motor exercies (at least 3x's per day!!!) and if all goes well - he'll be eating in a few weeks!

Another thing or 2 - the tube itself generally isn't removed until the Patient can "prove" they can eat/drink enough - this is usually by working up to not using it for a period of a few days to a couple weeks (excpet for the necessary water flushes)

Last thing, there is a small chance that the swallow may be permanently damaged and that the tube is a permanent thing. BUT, even if your husband does horribly on the MBSS that does not necessarily mean that he'll never eat again! When a swallow looks really bad it usually takes up to 2 years of work with the SLP, allowing for treatment and improvement over time before you'll have to/ should accept the remote possibility that he can't return to eating. Early intervention is key - glad to hear the MBSS is scheduled - that's the first step in the right direction!
Take care!