。
Ten years is a long time to wait.
Literal
10 years [topic-は] wait [purpose-には] long time [copula-だ].
The composite particle には here combines the purposive に ('for, in order to') with contrastive は. 待つには means 'for waiting,' 'in the context of waiting.' This は often draws contrast with other purposes: 'For waiting, ten years is long (though it might be short for other things).' A compact and idiomatic phrasing.