It's not accurate to say that a Spanish speaker will *ever* be able to speak fluent English. Some people learn English very well, while others struggle. It depends on various factors like:
* Motivation: How strongly do they want to learn?
* Exposure: How much exposure to English do they have?
* Learning strategies: How effectively do they learn new languages?
* Talent: Some people are naturally more gifted at language learning.
However, with enough effort and the right approach, any Spanish speaker can learn to speak English fluently.