Adam Clarke on Hebrews 11:40

God having provided some better thing for us - This is the dispensation of the Gospel, with all the privileges and advantages it confers.

That they without us should not be made perfect - Believers before the flood, after the flood, under the law, and since the law, make but one Church. The Gospel dispensation is the last, and the Church cannot be considered as complete till the believers under all dispensations are gathered together. As the Gospel is the last dispensation, the preceding believers cannot be consummated even in glory till the Gospel Church arrive in the heaven of heavens.

There are a great variety of meanings put on this place, but the above seems the most simple and consistent. See Rev 6:11. "White robes were given unto every one of them; and it was said unto them, that they should rest yet for a little season, until their fellow servants also, and their brethren, that should be killed as they were, should be fulfilled." This time, and its blessings, are now upon the wing.