この英語の文章は構文にできます。
「明日彼は会社を休む確率が高いと思います」
The chances that he'll be late for work tomorrow are high.
The chances of his being late for work tomorrow are high.
There's a strong possibility that he'll be late for work tomorrow.
It's very likely that he'll be late for work tomorrow.
He'll probably be late for work tomorrow.
It's very possible that he'll be late for work tomorrow.
など
~ の確率が高い : there is a high chance / there is a high probability / most likely
会社を休む : to be absent from work / to take a day off
1) There is a high chance that I will be absent from work tomorrow
There is a high chance that I will take a day off tomorrow
2) There is a high probability that I will be absent from work tomorrow
3) I will most likely be absent from work tomorrow
be very unlikely to V「Vする可能性がすごく低い」の意味です。
なので、
これを使って、
He is very unlikely to come to work tomorrow.
とすれば、
「彼は仕事に来る可能性がすごく低い」、つまり、「休む可能性がすごく高い」という意味になります。
2つ目の
He is very likely to take a day off tomorrow. は、
素直に「彼は明日休みを取る可能性がとても高い」の意味です。
ちなみに、
Timさんの
he'll be late for work tomorrow は、「仕事を休む」ではなく、「仕事に遅刻する」の意味です。