~(으)ㄹ 텐데 – Could, Would, Think it will be

(~ㄹ 테다, 테이다 – to be expected (conveys expectation, anticipation, intention, plan))

예약되어 있을 텐데요 – I believe I have a reservation. 
시속 40킬로로 달리고 있었을 텐데요 – I was going 40 kilometers an hour.

나 빼고 먼저 시작했으면 좋았을 텐데 – You should have started without me. (it would have been good if)
조금 더 일찍 깨워 줬으면 좋았을 텐데 – You should have woken me sooner. (if would have been good if) 
새라면 좋을 텐데! – I wish I was a bird! (it would be good if)
내가 돈이 있으면 그 것을 살 텐데 = I would buy that if I had money
음식이 더 있으면 좋을 텐데 = It would be good if there was more food
친구가 빨리 왔으면 좋을 텐데 = It would be nice if my friend came quickly
우리가 같이 갈 수 있었으면 좋았을 텐데 = It would be nice if we could go together

I suppose, it’s probable, i would imagine, i would think, must be

(slightly more certain than ~는 것 같다, and with a slight feeling of being worried.) 

비가 올 텐데 = It will probably rain (I suppose that it will rain)
날씨가 추울 텐데 = The weather will probably be cold
그가 집에 없을 텐데 = He probably won’t be home
그 식당이 이미 닫았을 텐데 = The restaurant is probably already closed
퇴근시간이라서 길이 막힐 텐데 = The roads will probably be jammed because it is rush hour
동부에 단풍이 한창일 텐데(요) = The fall foliage must be wonderful in the East.

~ㄹ/을 텐데, 테니까 – since it is expected, since it is probably that

(pretty much the same as~ㄹ/을 것 같아서)

그 식당이 이미 닫았을 텐데 가지 말자 = The restaurant will probably already be closed, so let’s not go
길이 막힐 텐데 지하철로 가자 = The roads will probably be jammed, so let’s take the subway
우유가 없을 테니까 하나만 사세요 = We probably don’t have any milk, so buy one

걸어가야 할 테니(까) 편한 신을 신으세요 = Since we’ll have to walk, please wear comfortable shoes.
내일까지 다 마칠 테니(까) 너무 걱정하지 마세요 = I’ll finish them all by tomorrow, so don’t worry too much
날씨가 추울 테니까 두꺼운 옷을 입고 나가세요 = The weather will be cold, so go out with thick (warm) clothes on
버스 타면 늦을 테니까 지하철을 타자 = We’ll be late if we take a bus, so let’s go by subway.