Let’s begin by looking at the Catechism:
1534 Two other sacraments, Holy Orders and Matrimony, are directed towards the salvation of others; if they contribute as well to personal salvation, it is through service to others that they do so. They confer a particular mission in the Church and serve to build up the People of God.
1535 Through these sacraments those already consecrated by Baptism and Confirmation for the common priesthood of all the faithful can receive particular consecrations. Those who receive the sacrament of Holy Orders are consecrated in Christ’s name “to feed the Church by the word and grace of God.” On their part, “Christian spouses are fortified and, as it were, consecrated for the duties and dignity of their state by a special sacrament.”
The vocations of marriage and holy orders are different but that does not mean one is greater or lesser than the other. St. Paul’s passage about many parts but one body (1 Cor 12:12-26) would seem applicable here. Permanent Deacons are expected first and foremost to be good husbands and fathers (if applicable) before they are considered for the permanent diaconate. They should be able to fulfill both their roles as husbands/fathers and deacons in order to be considered. One calling should not suffer at the expense of the other.
Different vocations should not be at the expense of one another. The calling to be a husband or wife should not detract from the calling to be a father or mother. All callings/vocations from God are complimentary not contradictory.
Permanent deacons are not required to abstain from marital relations.
Could this change? Its possible but not probable. The Church doesn’t change things merely for the sake of change or because someone thinks a change would be nice. Change comes only because through a well thought out process the proposed change is perceived to address a particular serious need/issue that the Church is facing. In this situation there is no real reason to change the allowance of married deacons and marital relations.
For further reading: Pope Paul VI’s General Norms for Restoring the Permanent Diaconate