Suppose we want to translate the whole of Wikipedia from English into Lojban, what are the main known big limitations or concerns we should be aware of? In other words, does Lojban as a language have sufficient expressive power for being translated from English?
A few things. First, Lojban often needs longer sentences to express something than it does in, for example, English.
Secondly, Lojban's vocabulary isn't that big, especially in the domain of sciences. Words would have to be calqued, adapted from English, French, etc. or completely re-invented.
Loaning and naming
Thirdly, the English language (and many natural languages) loans words directly (for example, champagne could be *shampain and buoy could be *boy or *boi) without changing spelling (a slight counterexample would be German, which often changes the letter c pronounced [k] to the letter k, like Kanada and Vokabular).
Lojban doesn't. .romas. is Rome (Italy), .xavanas. is Havanas (Cuba) and .lidz. is Leeds (UK). This makes it confusing in some cases. How would Lojban adapt Turra Coo or people like Nelson Rolihlahla Mandela? The name should stay recognisable but pronounceable.
One of Lojban's most famous features is, of course, its lack of syntactic ambiguity. While this is an advantage in some cases, it can also be a limitation. It wouldn't likely be an issue in something like Wikipedia, but does make certain kinds of wordplay impossible. Take for example this exchange from Lewis Carroll's Through the Looking Glass:
'Who did you pass on the road?' the King went on, holding out his hand to the Messenger for some more hay.
'Nobody,' said the Messenger.
'Quite right,' said the King: 'this young lady saw him too. So of course Nobody walks slower than you.'
'I do my best,' the Messenger said in a sulky tone. 'I'm sure nobody walks much faster than I do!'
'He can't do that,' said the King, 'or else he'd have been here first.'
In Lojban there is no way to conflate "nobody" meaning "no person" with "Nobody" meaning "someone named Nobody", because proper names are always preceded with the article "la". Other works that rely on wordplay based in syntactic ambiguity would also present major difficulties in translating to Lojban.
That said, there is a Lojban translation of Alice in Wonderland, so these difficulties aren't necessarily insurmountable.