Jamieson, Fausset and Brown on Isaiah 33:20

20. solemnities--solemn assemblies at the great feasts (see on Is 30:29; Psa 42:4; Psa 48:12).

not ... taken down ... removed--image from captives "removed" from their land (Is 36:17). There shall be no more "taking away" to an enemy's land. Or else, from nomads living in shifting tents. The saints, who sojourned once in tabernacles as pilgrims, shall have a "building of God--eternal in the heavens" (2Co 5:1; He 11:9, 10; compare Is 54:2).

stakes--driven into the ground; to these the "cords" were fastened. Christ's Church shall never fall (Mt 16:18). So individual believers (Re 3:12).