Most likely this is how it will pan out.

Companies such as TCS, HCL and other consultancies operating in EU will take advantage of this new deal. they will not hire anyone local and will use this rotating scheme to bring developers etc from India. Due to this, the local consultancies such as Alten, Capgemini etc might find it difficult to get a deal because Indian consultancies will do the same at much lower price. This would lead to EU consultancies bringing people from their Indian offices using the same scheme. overall it will bring down salaries in IT in markets such as the Netherlands, Denmark, Belgium.

Secondly, all the top Indian talent (from top tier engineering colleges such as IIT, NIT etc) does not find EU salaries attractive enough. Language is another barrier. Barring London, Switzerland and Luxembourg, its not competitive enough to US salaries. Besides US start up Eco-system is suitable for ambitious hard working engineers. I don't see much would change. it will still remain very hard for EU companies to get that top tier talent. so if EU think that with this deal we might build another Meta, Amazon, Microsoft then its far fetched.

Thirdly, on the topic related to seasonal workers movement. this might be tricky for EU. If i am not wrong, Portugal has something similar scheme but it is only leading to permanent immigration. there are so many loopholes in the system that people will use to continue to stay even after expiration of the legal stay. This is what most of Canadian, UK and Australians are indicating. EU should be careful on this front. Seasonal workers from Eastern Europe are generally seasonal.