I remembered Tonye T asked this question some years back. I gave this answer:

Pentecostalism will outlast protestantism, consume her. You would look to see Protestantism (That is if at all you would know what it had looked like then) and all you would see would be Pentecostalism. Pentecostalism would encroach  upon the mother church but she would withstand her!

And if you think pentecostalism you know today would be the same in ten years to come, you are in for a shock. Pentecostalism would continue to change and change like it has always done. It would absorb both the fair and the foul of her rapidly changing society. It would accommodate every wolf that comes into its fold with all cunningness and predatorship. All the believes of the new world order and more would be absorbed into penticostalism.

Penticostalism would grow and grow. This is because its going to become an easier option for the world of easy going humans, a world where nothing can be condemned, a world where people can no longer draw a line between sanity and insanity. It would become very attractive to members and lucrative to owners. Even as it is now, it would become more unchallenging to the consciences of its members and they would wallow in their iniquities, claiming grace for their purpose.

All forms of evil would be accepted as the norms because, penticostalism is based on personal perception of the Bible alone. No doctrine, no strict regulations, no laid down traditions, no established organisation that is superior to its founder, not even a formal training is strictly required. Men would rise up and interprete the bible the way that suits them, the way they want to believe it, like it has started already. The devil would call for miracle and innocent supposed but superior feeling christians would flock there. They would be spoken to sweetly, acted for beautifully, and dazzled with flints and sparkles. They would be told to believe and all these would be given to them! They would indirectly be encouraged to embezzle, steal and defraud (Grace covers them anyway!).

You ask, will pentecostalism last?! It will outlast most orthodox and protestant churches of today. It would assume an unchristian dimension, its form very attractive and alluring, like its already assuming. It would, in its thousand and one different forms be the main church beside the Catholic Church. It would become more worldly than the world. Pentecostals would believe themselves to be the real Christians, the heaven bound people. But may God help us!

You asked a question, here, you have an answer

So, what's your opinion?

What is the difference between Pentecostals and Protestants?

Actually, Pentecostals can be Protestants. They are mostly Protestants in the sense that they are not part of the Roman Church.

However, Pentecostals have a varied theological and practical essence. Practically, the Pentecostals emphasize a more emotional worship. Theologically, Pentecostals prioritize the miraculous or sign gifts. Many Pentecostals take the additional and errant steps of claiming that the indwelling of the Spirit is a 'second blessing' and in claiming that one must speak in tongues as evidence of having that blessing. The error of this Biblically, is seen in the Apostle Paul noting that all who believe in Christ have been baptized in the Spirit and yet not all speak in tongues (1 Corinthians 12,13).