You likely have the V6 motor, most Solaras have the V6.
You can postpone the repair as long as you want. Until the belt breaks the car will run fine. After the belt breaks is the problem.
No way to tell the condition of the belt as it sits now.
If it breaks when you are on I-95; the motor stops suddenly, your power steering stops when the motor stops so steering is possible but it is very much harder to turn the wheel. You’ll have power brakes to stop the car once, then the brakes will get hard and ineffective. You’ll have to get to the side of the road “coasting” traffic will have to dodge around you. If you are in the middle or passing lanes it could be difficult to get to the right side shoulder before the car looses all momentum. If you are on a bridge you might have very little to no shoulder at all for an emergency pull over. Once you get to the side of the road you aren’t going anywhere without a tow. So, you need to know the number for your AAA service, other road side service, or a local tow company.
When you get the car to a shop the V6 motor will have internal damage to valves and pistons and you will likely need to purchase a new or rebuilt motor and have it installed in the car. The old motor will be broken beyond a reasonable repair cost. You will be looking at about $3,000 to get the car on the road again.
Suggestion- replace the belt now. If you wish drive on, but be ready to buy another car when the belt breaks. If you can’t afford the cost of a new belt, I don’t know how you can afford to buy another car either.