My friend (in Canada) and I (in South Korea) have conceded that we won’t be attending Gencon this year. We had rooms booked months ago and were looking forward to attending again (this would have been our sixth Gencon), but with the way foreigners are being detained and turned away at the border, it’s not worth risking thousands of dollars for prepaid rooms and flights to take the chance. Additionally, we were discussing how expensive the new games would be this year, given the massive tariff markups that are in place.
Between the two of us, we would have spent close to ten thousand dollars for the trip.  I also wonder if any foreign game companies will be able to afford to attend and bring their product to the con. 
This is not meant to be a political post; I’m just curious how other people feel about how the current situation will affect the con and the games in general. 

I think there is a lot of misinformed hysteria being sensationalized for engagement of online financial opportunity (clicks) and we have all been inundated with its fallout.

More to your actual questions:

Companies have already paid for their spot on the show floor and while they could ask for a refund they will likely be moved to the non-renewing vendor list for next year and have to apply for a new spot allocation. I cannot speak to any companies financials but it is often better to just not show than cancel (and potentially lose out on lower renewals or even a spot next year).

As for actual product; I am 50/50 on what we will see. I expect business as usual with a higher price point for major vendors and a lot of older stock (previously imported) for smaller ones. Overall the price of goods for these vendors is going to be interesting to see as they cannot maintain the previous profit margin so will need to test the customer on how much they are willing to spend for new product and if they will try and apply "tariff pricing" on previously imported product. In short if a game MSRPs for 30$ American the vendor will not try and sell it 67.50$ (125%) because the market just will not accept it.

Looking at the news American imposed tariffs across the board are already being lowered, which is good as I think tariffs should be used like a scalpel instead of a war hammer on countries imposing them on others. Though I am also pretty disgusted with how quickly a lot of gamers got real cool real fast with low wage labor because their click clacks now cost more (at least vocally online).