Microsoft agreed to buy Nokia's hardware business (i.e. Lumia phones) on September 3rd, but the deal has not closed yet. Until Microsoft officially takes them over (which should be soon), the engineers, development and production line have to work on something. It's not like they were fired, or given 4 month vacations. Besides, deals sometimes fall apart or do not get government approval. If Nokia produced nothing new during this transition, and the deal fell apart ... they would be screwed.