Transpose "hope" and "expectation." The expectant waiting of the righteous is joyful at the time, and ends in joy: the eager hope of the wicked comes to nought.

The expectation of the wicked shall perish - A wicked man is always imposing on himself by the hope of God's mercy and final happiness; and he continues hoping, till he dies without receiving that mercy which alone would entitle him to that glory.

The hope of the righteous shall be gladness,.... Or, "is gladness" (w); it is now attended with joy; he has a pleasure in the exercise of the grace of hope as to future things; he rejoices in hope of the glory of God, and is enabled to hold fast the rejoicing of his hope firm unto the end, Romans 5:2; and the issue of his hope will be an abundant entrance into the joy of his Lord; a being brought into his presence, in which is fulness of joy; he is not ashamed of his hope now, and he will not be disappointed hereafter;
but the expectation of the wicked shall perish; his hope and expectation, either of riches, and honour, and pleasure in this world, or of a long life in it; or of happiness in the other, and of escaping the wrath of God, and the vengeance of eternal fire; all which, being grounded on a wrong bottom, shall be frustrated; see Job 8:13.
(w) "Esther", Pagninus, Junius & Tremellius, Piscator, Michaelis.

gladness--in confidence of realizing it.
expectation . . . perish--in disappointment.

28 The expectation of the righteous is gladness
And the hope of the godless comes to nothing.
תּוחלת as well as תּקוה proceed on the fundamental idea of a strained earnest looking back upon something, the same fundamental idea which in another view gives the meaning of strength (חיל, Arab. ḥayl; ḳuwwat, kawiyy, cf. גּדל, Arab. jdl, plectere, and גּדול, strong and strength). The substantival clause 28a denotes nothing more than: it is gladness (cf. Proverbs 3:17, all their steps are gladness), but which is equivalent to, it is that in its issue, in gaudium desinit. Hitzig's remark that תוחלת is the chief idea for hope and fear, is not confirmed by the usage of the language; it always signifies joyful, not anxious, expectation; cf. the interchange of the same two synonyms Proverbs 13:7, and תּאות, Psalm 112:10, instead of תּקות (here and Job 8:13). While the expectation of the one terminates in the joy of the fulfilment, the hope of the other (אבד, R. בד, to separate) perishes, i.e., comes to nothing.

Gladness - Shall be accomplished, and turned into enjoyment.