By the time your course ends, you'll have both your degree and multiple years of experience – and all at the expense of your employer. So most companies will want to retain the talent they've invested so heavily in.
Depending on the course and company, you may automatically be offered a role or you may need to apply for open roles. However, either way you're likely to be in a strong position and you should know enough about your employer to know where you'd like to work permanently.
Though if you've fallen out of love with the place, or there are no positions to apply to, you will of course be free to leave and go elsewhere. Just be slightly wary as some companies will have a clause in your contract which could mean it's able to claw back the costs of your studies if you leave within a certain timeframe, or before the course is finished. Plus, if you leave before completing, you won't have earned your full degree.
For example, if you leave within a year of the course ending you could be asked to repay 50% of the tuition fees, within two years 25% and within three years 10%. We have heard of cases where companies haven't enforced this in practice, but it's something to bear in mind.